The present invention arose in response to a situation that could not be met by existing equipment. Specifically, the situation was the ditching of helicopters, and subsequent capsizing, particularly in cold water.
It was found that when a helicopter ditched it almost immediately turned over, due to the weight of the engine and transmission on the top of the fuselage. Although the helicopter's flotation gear ketp it from sinking, the crewmen were trapped in the cockpit or cargo compartment and were immersed in approximately 6 feet of water. The pilot and co-pilot were quite often still strapped in their seats, not having had time to release themselves before ditching.
It was further found that in some ditchings several crewmen drowned when it seemed that they should have been able to escape. Tests then showed that because of the low temperature of the water the men could not hold their breath as long as they could in warmer water, hence the drownings. This was further compounded by the fact that some were strapped in, which presumably led to a slight panic and which in turn further reduced their ability to hold their breath.
Another problem with escaping from a ditched helicopter is that sometimes the person will have to swim downward to a small hatch and wiggle through it in order to get to the surface. This means that a conventional large personl flotation device, which as a large amount of positive buoyancy and bulk, can hamper the wearer in two ways; the buoyancy can inhibit his ability to swim downward to the hatch, and the bulk of the device can make it difficult to squeeze through the hatch once he gets to it. These facts added to the problems of being strapped into a seat and being immersed in cold water result in a situation that is much more severe than it would seem to be.
A helicopter is a relatively small vehicle, and the distance to be covered to escape from any point within it is very small. Thus an escape device does not need to contain more than two or three minutes of breathing capability, to allow the escaping person to fight off any panic that may set in. It also should be relatively small, and low in buoyancy, to allow the person to squeeze through a small escape hatch. However, it should also be large enough to keep a person afloat in case rescue is not very quick.